Logic Answers

8/19/2019 Logic Answers

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218

ANSWERS TO SELECTED EXERCISES

CHAPTER ONE - INTRODUCTION TO CRITICAL THINKING

No answers are given for the exercises in chapter one. These exercises are best used as the focus of essays and discussions toget the class members involved in the course process and to make sure they understand what the course is about and what they

can expect to gain from a course that emphasizes critical thinking.

Chapter One Self-test

1 T

2 T

3 F

4 T

5 F

6 T

7 T

8 T

9 F

10 F

11 F

12 F

13 F

14 T

15 F

16 F

17 F

18 F

19 F

20 T

21 T

22 F

23 F

24 F

25 F

26 F

27 F

28 T

29 T

30 T

31 T

32 T

33 F

34 T

35 F

§

CHAPTER TWO - LANGUAGE AND CRITICAL THINKING

EXERCISES 2-1

A. 2. (old): ‘dilapidated’, ‘ antiquated’, or ‘aged’ (more negative); and ‘patriarchal’, ‘seasoned’, or ‘antique’ (more

positive). 7. (plan): ‘scheme’ or ‘plot’ (more negative); ‘organize’ or ‘devise’ (more positive). 10. (take): ‘steal’

(more negative); ‘appropriate’ (more positive).

B. 1. (stink): odorous; 4. (shy): restrained; 6. (murder): ‘termination’.

EXERCISES 2-6 C

1. This ad makes it sound as if ‘chemicals’ cannot be used for bad purposes, like making napalm or other chemical

weapons.

6. What could it possibly mean for a cigarette to taste as good as it looks? The expression here has no cognitive

meaning, but it sounds like a good thing.

11. Why should hair shine?

EXERCISES 2-7

1. ‘Brutality’ is vague because there is no clear and definite boundary separating acts of brutality from acts which do

not involve brutality. The expression ‘police brutality’ might be made clearer by providing some criteria as to what

constitutes police brutality. However, most criteria--such as "the use of unnecessary force causing pain or discomfortto one being arrested"--will probably lead to other vague terms--such as ‘unnecessary force’--needing clarification.

Best might be a partial list of the kinds of cases which constitute brutality, such as the use of deadly force on an

unarmed suspect or the breaking of a suspect’s arm while putting on handcuffs. Any criteria, however, are bound to

be vague to some extent.


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2194. This kind of claim is frequently made by government officials. ‘Near future’ is the kind of expression which could

be replaced with a more specific one, such as one which gives a date or range of dates (e.g., ‘by next December 1st’

or ‘between next June and next October’).

EXERCISES 2-8

1. This is a good definition of ‘cetacean’.

2. This definition is too broad. It would include in its denotation many persons who are not demagogues, namely,

those with charisma who do not use their charm and powerful personality to play upon the basest fears and

prejudices of people, which is what a demagogue does.

3. On one level, this definition may be good, namely, on the level of the novel: if the definition fits the character

giving it, then the definition is a good one. However, as a definition considered in and of itself, this one is too

narrow. It excludes from its denotation what most people would consider to be essential to free speech, namely,

speech which criticized the government.

4. This definition would be both too broad and too narrow. It is too broad because it includes in its denotation people

who drink two or more beers a day and are not alcoholics (such as sumo wrestlers). It is too narrow because it

excludes from its definition those who drink other kinds of alcoholic beverages besides beer but are alcoholics. It

also excludes those who are alcoholics and who drink no alcohol!

5. This definition is packed with theoretical assumptions and implications. It excludes human fetuses and comatosehumans from its denotation. This may be acceptable to some people, but it is a consequence of the definition which

might lead others to reject it.

6. This is a common, but greatly flawed definition of ‘spirit’. It is too vague because it tells us what a spirit is NOT

rather than what a spirit is.

7. Many students will find this definition obscure. A careful examination of it, however, reveals that it is a humorous

way of saying that the word ‘depression’ has such great negative emotive content that economists and politicians

would rather use a milder word, ‘recession.’ (By the way, Galbraith is aware that economists give technical

definitions of the two terms and consider a recession and a depression to be distinct.)

9. This definition of ‘aggression’ is too narrow; it excludes verbal attacks, for example.

18. This definition is too vague. What is a reasonable man in present-day Western society?

EXERCISE 2-9

1. stated as a fact and is a strong claim.

2. stated as a fact and is a very strong claim

4. stated as a fact and is a very strong claim.


6. stated as an opinion and is a strong claim.



11. stated as an opinion and is a strong claim

15. stated as an opinion is a weak claim

16. stated as facts and stated weakly. (Don’t be misled by the use of will, which seems to indicate a strong claim. The

weasel words as much as make the claim a weak one.)

17.stated as an opinion and is a weak claim

21. stated as a fact and stated very strongly25. stated as an opinion and stated weakly

30. stated as a fact and stated very strongly


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220EXERCISE 2-10

1. F

2. F

3. T

4. T5. F

6. F

7. T

8. T

9. T

10. T

11. T

12. T13. T

14. T

15. T

16. T

17. T

18. T

19. F

20. T21. F

22. T

23. F

24. T

25. T

26. T

27. T

28. T29. F

30. T

31. T

32. F

33. F

34. T

35. T

36. T37. T

38. T

39. T

40. F

41. T

42. F

43. F

44. T45. T

§

CHAPTER THREE - SOURCES

EXERCISES 3-1

1. What president hasn’t made such claims? Such claims are about as trustworthy as long range weatherforecasts. The subject matter is very controversial, very complex, and what is being predicted is on shaky grounds.

Most presidents are not economists (so this source is probably not an expert), but even if an economist made this

prediction, it would be wise to take it with a grain of salt (i.e., suspend judgment). Note that these weakly stated

empirical evaluations are couched in vague language: ‘as much as’ leaves room for everything from 0 to the

percentages stated. Furthermore, no deadline is stated. When are these effects on inflation and unemployment

supposed to be felt? Finally, the likelihood of being able to show that any change in inflation or unemployment was

caused by the president’s policies is slim, indeed. The claims are practically meaningless.

3. expert; biology is a non-controversial field (experts agree on fundamental facts and methodologies); she is

stating her opinion and it is a weak one, a statement of mere possibility, so I would accept it based upon the general

knowledge that environmental pollution is a common problem in our society; it seems reasonable to believe that the

state of California requires that its biologists have the proper degrees and credentials; to know more about this

particular state biologist’s reliability I would need to know her reputation in the field.

6. No special expertise is needed for this claim. If the newspaper is reliable, there would normally be no reason todoubt this claims which are put forth as facts. (Note: there are 2 facts claimed here: (1) that there were 3 stabbings;

and (2) that inmates stabbed inmates. Either of the claims could be inaccurate, of course; and, barring any special

need to believe one way or the other on this issue, it might be wise to suspend judgment until there is further

corroboration from other reports; if the story has a byline you can tell who authored it and you would need to know

that writer’s track record on accuracy to determine his or her reliability; otherwise, you must consider only the

reputation and track record of the newspaper itself.

8. non-expert; stated as a fact and stated strongly; his claim is credible (it is, unfortunately within the realm of

possibility that our government would do such a thing) but I would suspend judgment on it because the source

should be considered unreliable due to the strong possibility that it is propaganda; I would not concern myself with

this source any further but would seek out more objective parties for further information.

11. expert; controversial field; his claim is stated as a fact but it is a metaphysical claim; thus, even after

determining the reputation of this philosopher, I should study other equally reputable philosophers with different

views on the subject before making up my mind on this issue.13. non-expert. It seems to me that Mr. Coleman ought to seek other means of employment if he thinks comets

are causing teenage suicides and airplane crashes. Mr. Coleman’s opinions about the connection between Halley’s

comet and teenage suicides and airline crashes are incredible and ought to be rejected. He may be an expert on

suicide prevention, but his claims are well outside of that field. These tragic events also coincide with the fall from

first to last place of the Chicago Cubs and with Ronald Reagan’s term of office (and with many other things as well).

I would not concern myself further with this source on astrological or paranormal matters.

15. you are told the source is an expert; the field of economics is controversial; the claim is clearly this person’s


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221opinion stated as a fact, but it is stated weakly (note the weasel words "as much as"). The expert is saying that

interest rates will not drop by more than ten percent in the next six months--a pretty safe claim under most

conditions. I would say that if one has no knowledge of interest rates that one should suspend judgment on the claim.

But anyone knowing the history of interest rates in recent years would know that the expert is asserting something

about as extraordinary as claiming that the average price of a new home will not drop by more 10 % next month.

That would be a very weak claim, indeed. One shouldn’t reject it. To suspend judgment seems unnecessary. Aknowledgeable person would not ask for proof of such a claim and would accept it because it is a pretty safe bet. To

determine this person’s reliability, one would have to establish that he or she is really a qualified economist. One

would also want to know his or her track record in the area of predications about interest rates and other related

matters.

19. Most likely a non-expert (journalist) is reporting on the claims of experts (the doctors and scientists). Both

the non-expert and the experts are putting forth their claims as facts. Medicine is a mixed field; some areas are

controversial and other areas are not. There would normally be no reason to doubt the report that the doctors made

the claim they are said to have made about the over-use of antibiotics. The fact that the doctors issued statements in

several cities around the world indicates their belief in the urgency of the message. But should one believe--solely on

the basis of this report--that antibiotics are being overused throughout the world, and because of this are losing their

disease-fighting power? Having no reason to doubt their claim and having some experience with antibiotics

becoming ineffective because of extended use, I would accept the claim as probably true. If you have no knowledge

of antibiotics, you should suspend judgment until you learn a little more. You would not likely be able to determinethe reliability of each of these expert sources. See the answer to number 6 above for determining the reliability of the

journalist.

23. Expert; controversial field; stated as a fact but the claim is a self-assessment of her evidence and is a strongly

asserted opinion. One ought to suspend judgment, regardless of the reliability of the source, until one sees the

evidence. There is no reason to suspect that the source here is unreliable. Her degrees, credentials, reputation should

be considered, but opposing experts should also be considered.

25. Woodford is presented as an expert speaking in his field. The claim he makes about melanin and marijuana

having a similar chemical structure is stated as a fact and is not likely to be in a controversial area of chemistry, since

it involves only comparing the chemical structure of two substances. It would therefore be reasonable to accept it as

probably true. Woodford is also an expert in drug abuse court cases. His conclusion that drug urinalysis may be

inaccurate for dark-skinned people is equally reasonable, as it is a weakly stated empirical opinion by an expert. The

reliability of a chemist would be determined by degrees, credentials, experience and reputation.

EXERCISE 3-3

1 T

2 T

3 F

4 T

5 T

6 T

7 F

8 T

9 T

10 T

11 F

12 T

13 F

14 F

15 T

16 F

17 T

18 T

19T

20 T

21 F

22 T

23 T

24 T

25 T

26 F

27 T

28T

29 T

§

30 T

31 F

32 T

33 F

34 T

35 T

36 T

37 T

38 T

39 F

40 T

41 T

42 T

43 F

44 T

45 F

46 F

CHAPTER FOUR - IDENTIFYING ARGUMENTS

EXERCISE 4-1

1. This is a complete sentence which makes a statement, so it could be used as premise or a conclusion in an

argument.


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2225. This is a fragment of a sentence; it does not make a statement, so it could not be a premise or a conclusion in

an argument.

8. This sentence makes a statement. It could be used as a premise or a conclusion.

12. This is a fragment of a sentence. It does not make a statement. It cannot be used as a premise or a conclusion.

15. This sentence makes a statement. It could be used as a premise or a conclusion.

EXERCISE 4-2

1. premise : Justice is nothing but the way the rich protect their interests.

conclusion: Justice can’t exist for the poor.

premise indicator : because

5. premise : Size is irrelevant to intelligence.

conclusion : You are wrong in stating that women must be less intelligent than men.

premise indicator : because

conclusion indicator : it is necessarily the case that

10. premise: He died before his twentieth birthday.

conclusion: King Tutankhamen was not a great king.

premise indicator: because

14. premises: Astronomy was born of superstition; eloquence of ambition, hatred, falsehood and flattery; geometr

conclusion: The arts and sciences owe their birth to our vices.

conclusion indicator: Thus

EXERCISE 4-3

There are several correct formulations for each of these.

1. Since immorality has to stop somewhere and because decent people have to start standing up for their rights,

nude bathing should not be allowed.

6. There is nothing in the Bible which forbids slavery. The Bible is the word of God. Therefore, slavery was

ordained by God.

EXERCISE 4-4 1. premise : "Such a law would allow government to substitute its laws for our freedom to make individual

decisions."

premise : "It didn’t work with liquor prohibition"

premise : "it won’t work with smoking prohibitions."

conclusion : "There should be no law which regulates when and where an individual may smoke."

6. premise : "My first four husbands were insecure babies"

conclusion : "Men are all insecure babies"

9. premise "As Superintendent of Schools, you have a vested interest in the funding bill before this legislative

committee."

conclusion: "Your arguments for increased funding of the public school system may be justifiably ignored."

12. premise: No one ever did anything he or she did not want to do.

conclusion: If Smith robbed that bank, then he wanted to do it.

15. premises: If fatalism is true, then everything that happens has to happen. If no one can change what must happen,

then there is no sense in worrying about what happens, whether it is good or bad.

conclusion: Fatalism should take away our worries.


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EXERCISE 4-5 A

1. premise : It might lead to psychosomatic illness or it might result in anti-social behavior"

conclusion : "Holding in one’s feelings in not healthy"premise indicator : "since"

7. premise : "Either it will rain or it will snow."

premise : "It will not snow."

conclusion : "it will rain."

conclusion indicator : "Therefore"

11. premises: If the President is telling the truth then the Russians will not invade Poland. The Russians will invade P

conclusion: The President is lying.

conclusion indicator: So

12. premises: Either the Germans not will quit the United Nations or the moon will turn to green cheese. The moon

will not turn to green cheese.conclusion: The Germans will not quit the United Nations.

conclusion indicator: it follows that

EXERCISE 4-5 B

1. The conclusion of this argument is ‘There must be simple substances.’ ‘Because’ and ‘for’ are indicators.

‘There are composites’ and ‘a composite is nothing else than a collection or aggregate of simple substances’ are

premises.

2. This is not an argument.

3. This is not an argument; it is a conditional statement.


8. The conclusion of this argument is ‘memory should not be trusted as the sole judge of the truth of any claim.’

The premise is ‘memory is fallible and memory sometimes is constituted by later acts.’ ‘Since’ is a premise indicator.13. The premise of this argument is ‘She did well on the exam.’ The word ‘so’ is a conclusion indicator. The

conclusion is ‘she will graduate.’

16. This is a question. It is neither an argument, nor an explanation.

19. The conclusion of this argument is ‘[W]e ought mutually to tolerate one another.’ ‘Because’ is a premise

indicator. ‘We are all weak, irrational, and subject to change and error’ is a premise.

21. This is not an argument; it is a conditional statement.


27. The conclusion of this argument is ‘there must be life on Mars.’ ‘Since’ is a premise indicator. The premise is

‘nobody has been able to prove there isn’t life there.’

EXERCISE 4-7

In the answers to this set of exercises, premise indicators are italicized , conclusion indicators are boldfaced.

1. "Since [1][beauty] is no creature of our reason...[and] since [2]it strikes us without reference to use...we must

conclude that [3] beauty is, for the greater part, some quality in bodies acting mechanically upon the human mind by

the intervention of the senses."


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7. [1]Women are directly fitted for acting as the nurses and teachers of

our early childhood by the fact that [2]they are themselves childish,frivolous and short-sighted;[3]in a word, they are big children all their

life long....

12. [1]No educated man stating plainly the elementary notions that every educated man holds about the matters that

principally concern government could be elected to office in a democratic state, save perhaps by a miracle. [2]Hisfrankness would arouse fear, and those fears would run against him;[3]it is his business to arouse fears that will run

in favor of him.

19.[1]I just don’t see why multicultural education is so popular or why people

think it is value-free. [2]Multicultural education is not value-free, despite what its

proponents say. [3]It teaches children to respect and accept the evil values and

practices of other cultures such as genital mutilation of young girls in Africa and

handing out death sentences for blasphemy in Iran.

23. [1]Restitution, rather than

imprisonment should be required in those cases where property damage

is the issue; for , [2]sending a person to prison ought to be avoided

whenever possible and [3]the victim of a property crime is likely to be

much more satisfied with our criminal justice system if he or she is

repaid. [4]If a criminal goes to prison, he is not going to be able to make

restitution. {Note that this argument assumes that the victim of property

crime is due some sort of satisfaction.}

1

2 3

No. 7

2

1

3

No. 19

1

2 3 4

No. 23


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225


EXERCISE 4-8

1.1= a; 1.2 = a; 1.3 = c; 1.4 = c; 1.5 = b;

1.6 = c (‘therefore’ is a conclusion indicator; ‘since’ is a premise indicator).

Note: Statements 3 and 4 are identical. Thus, here the same statement is used as

both a premise and a conclusion.

2.1 = d; 2.2 = b; 2.3 = a 2.4 = a (‘for’).

Note: Statement 1 is neither a premise nor a conclusion, so it is not diagrammed

as being linked to statements 2 and 3.

4.1 c (statement 2 supports 1 and 1 supports 3); 4.2 = a; 4.3 = c

(statement 3 is supported by statement 1 and supports statement 5); 4.4

= a; 4.5 = b (this is the main conclusion); 4.6 = a; 4.7 = c (‘for’ is a

premise indicator; ‘so’ is a conclusion indicator)

5.1= d; 5.2= a; 5.3 = b; 5.4 = b (‘therefore’) Note: This argument has an

unstated premise (UP): "There is disagreement about the Truth in the Holy Book."

5

3=4

1 2

No. 1

2

1 3

No. 2

5

3 4 6

1

2

No. 4

3

1 2

No 5.


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22611. There are two arguments in this passage. Argument

1 consists of statements 1,2 and 3.

11.1 = a; 11.2 = a; 11.3 = b;

Argument 2 consists of statements 4,5 and 6. 11.4 = b; 11.5 =

a; 11.6 = a; 11.7 = c (`thus’ is a conclusion indicator; ‘since’ is a

premise indicator)

12.1 d; 12.2 = b; 12.3 = a; 12.4 = c; 12.5 = a; 12.6 = c; 12.7 =

a; 12.8 = a (`for’).

Note that statement 1 is background information necessary for understanding the meaning of statement 2.

15. There are two arguments in this passage. Argument 1 consists of

statements 1,2 and 3.

15.1 = b; 15.2 = a; 15.3 = a;

Argument 2 consists of statements 4,5 and 6.

15.4 = b; 15.5 = a; 15.6 = a;

15.7 = a (both arguments use ‘for’)

EXERCISE 4-9

1 true

2 false

3 true

4 true

5 false

6 false

7 true

8 true

9 true

10 false

11 true

12 true

13 false

14 true

15 true

16 true

17 true

18 true

19 true

20 false

21 true

22 false

23 true

24 true

25 false

26 false

27 true

28 false

29 true

30. true

31. true

32. true

33. true

34. true

35. true

CHAPTER FIVE - EVALUATING ARGUMENTS

EXERCISE 5-1 A

1. Valid by modus tollens.

3. Valid by modus ponens.

6. Invalid; affirming the consequent.

12. Invalid; denying the antecedent.

14. Valid by hypothetical syllogism.

19. Valid by disjunctive syllogism.

3 4

1 2 5 6

No. 111 2

3 4 6

5 7

No. 12

1 4

2 3 5

No. 15


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227

EXERCISE 5-1 B

1. ‘He is responsible for the accident’ is the implied conclusion, derived by applying modus ponens to the two stated

claims.

4. The conclusion, "it’s not going to rain," could be validly inferred by modus ponens, assuming as an unstatedpremise Ìf she didn’t bring her umbrella then it’s not going to rain.’ This conclusion could also be validly inferred

by disjunctive syllogism, assuming as an unstated premise Èither she brought her umbrella or it’s not going to rain.’

7. `The soul must be made up of atomic particles’ is the implied conclusion, derived by applying modus ponens to

the two stated claims.

10. Ìf I buy a car, it means bye-bye education,’ derived by applying hypothetical syllogism to the two stated claims.

EXERCISES 5-2 A

1. ad populum and appeal to guilt

3. argument from ignorance

5. ad hominem

8. ad hominem

10. questionable assumption12. appeal to vanity

15. poisoning the well

18. appeal to fear

20. questionable assumptions

23. This is an irrelevant comparison. The shipyard workers were exposed to large quantities of asbestos fibers in the

air. The asbestos in insulation or tile is not free floating until one tries to remove it!

EXERCISE 5-2 B

1. ad populum, poisoning the well; argument from ignorance and irrelevant appeal to authority

4. Hayakawa evades the issue by making an irrelevant comparison and an irrelevant appeal to authority.

6. ad populum

8. ad populum and appeal to authority (also, it is irrelevant to the issue to bring up what the Pentagon spends ontanks and airplanes)

11. questionable assumptions

EXERCISE 5-4 A

1. loaded question

2. false dilemma

5. begging the question

7. invalid by denying the antecedent

10. non sequitur; though, perhaps the arguer is making the questionable (and unstated) assumption that the

government should pay for whatever medical services an individual can’t afford on her own.

11. The truth of the stated premise depends upon its meaning. If it means that the average height of women is lessthat the average height of men, then the statement is true. If it means that every woman is smaller than every man,

then it is false. There is an unstated premise here--that whoever is larger is stronger--and this is a questionable

premise.

14. invalid by affirming the consequent



20. These premises are warranted, relevant and sufficient to support their conclusion..


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22821. suppressed evidence

22. false dilemma (perhaps meanings don’t reside anywhere and aren’t in anything. Maybe meanings are a function

of the usage of words.)

23. begging the question. The arguer has assumed that this candidate is like most politicians, in addition to assuming

that most politicians can’t be believed.

24. appeal to authority27. The arguer begs the question as well as poisons the well. He assumes what should be proved, viz., that abortion

is murder.

28. slippery slope

EXERCISE 5-4 B

1. questionable assumption; begging the question

3. questionable assumption; hasty conclusion

4. questionable assumption (that abortion is the slaughtering of children); questinoable claims; slippery slope

5. The premise is a statement of logical possibility. It would be false only if it contained a self-contradiction (such as

`round square’ or `married bachelor’). The assumption is relevant to proving the conclusion and is sufficient as well.

Thus, this is a sound argument.8. The first premise--èither there is no afterlife or there is one’--is a tautology; it is necessarily true. The second

premise --ìf there is none, then it is absurd to believe in punishment after death’--follows necessarily from the

tautology and its implications and is therefore also true. But the third premise--that àn all-just and all-merciful God

would not punish a creature for being too weak to resist desires instilled by the Creator’--is a metaphysical claim and

is questionable. It assumes that if there is a God, God is all-just and all-merciful. It assumes, in fact, the very issue

that ought to be proved, viz., that God won’t punish anyone. Thus, the argument begs the question.

9. poisoning the well and straw man. To argue against giving the Contras money is not to advocate communism; so

the refutation distorts the view of his opponent. And the refutation tries to associate the opponent with something

considered evil.

12. Good argument, though it would be better if it were clearer what is meant by without meaning to our minds. I

take Hocking to mean that each of the alternatives is inconceivable. The premises seem true, relevant and sufficient.

14. questionable claims; slippery slope

17. The premises seem clear enough, relevant to demonstrating that the `liberals’ are wrong about the rich payingtheir fair share of taxes, but the evidence isn’t sufficient because Buckley suppresses relevant evidence. Buckley

doesn’t reveal either what amount or what percentage of the earned income the 3 percent account for. If those 3

percent account for 62 percent of the nation’s earned income, then they’re only paying half as much in taxes as they

should. Or if 97 percent of the people account for 35 percent of all earned income but are paying 69 percent of all

taxes, then the rich are paying a lot less than their share in taxes than the rest of us.

19. poisoning the well and straw man. The opponent distorts proponent’s view and tires to associate it with evil.

EXERCISE 5-4 C

1. straw man; the letter distorts Mondale’s position.

3. begging the question (Brennan assumes that executing a person denies their humanity, but that is the issue he

should be proving, along with the assumption that denying a person’s humanity while punishing that person

constitutes cruel and unusual punishment.)5. seems like a reasonable argument to me

6. This rambling letter in support of the candidate not in office contains some warranted claims but it also makes

some questionable claims (e.g., if we re-elect the president we’ll either go bankrupt or have the highest tax rate in

the world and nobody is better off today... Also, even if it is true that the president’s opponent is sincere and honest

(which might be questionable), it wouldn’t be sufficient reason to vote for him or to believe that things will be any

better under his administration. Finally, the concluding claim is a bit ambiguous. If the president were re-elected, his

supporters would agree that the election resulted with "what’s best for the United States"!


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2298. The sponsors of this ad wrongly accuse the EPA of demanding an unreasonable procedure: measuring pollutants

as they come out of a smoke stack. If they were measured on the ground, what would be measured? The ad seems to

say that it is irrelevant what measurements are made at the top of the stack. I don’t think so. What would be

irrelevant would be to provide data about pollution at the bottom of the stack on the ground or on the ground in the

next town over. The only way to know what the source of the pollution is would be to measure it at the source!

Imagine trying to convince someone doing a smog check on your car to put the measuring device across the street

instead of up your exhaust pipe!

10. This is about as good an argument as one should reasonably expect in a letter to the editor. Of course, the letter

writer assumes the reader has some basic background knowledge--a reasonable assumption, since the reader of the

letter is a newspaper reader.

12. questionable assumptions about what a newspaper is supposed to be doing; begs the question

15. loaded language, suppressed evidence, questionable claims, appeal to fear

EXERCISE 5-5

1 true

2 true

3 false

4 false

5 true

6 false

7 false

8 true

9 true

10 true

11 true

12 false

13 true

14 false

15 false

16 true

17 true

18 true

19 false

20 false

21 false

22 false

23 true

24 true

25 true

26 false

27 true

28 true

29 false

30 true

31 true

CHAPTER SIX - EVALUATING EXTENDED ARGUMENTS

EXERCISE 6-1

1. Unstated: "We don’t make the car payment," and "We don’t want to get kicked out into the streets."

2. Unstated: "The Reds came in second."

CHAPTER SEVEN - SAMPLING

EXERCISE 7-1

1. false

2. true

3. false

4. false

5. false

6. true

7. false

8. true

9. false

10. false

11. true

12. true

13. false

14. true

15. true

16. true

17. false

18. true

19 true

EXERCISE 7-4

1. Unrepresentative sample. The method used is not likely to give a good cross-section of the voting population.

5. Hasty generalization.


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EXERCISE 7-8

1. This argument is based on the assumption that there are countless planets, an assumption itself based on analogical

reasoning. For, these countless planets have not been observed. But, given our knowledge of the origin and nature ofour own solar system, it seems reasonable to assume that of the countless stars in the countless galaxies, there are

countless planets, some about the age and size of earth and in relation to a star as we are to our sun. If this

assumption is granted--and it seems reasonable to assume so, otherwise we would need to justify believing that our

solar system’s origin and nature is unique and not likely to be representative of the rest of the universe--then the

conclusion is a sound one. Note the language used to express the degree of probability of the conclusion: "there may

very likely exist...." The language is appropriate for the evidence.

10. The lawyer ignores a relevant and highly significant difference between the two kinds of testing. The one is to

prevent epidemics of contagious diseases; the other is to catch criminals and punish them. Thus, the fact that

tuberculin testing is justifiable in no way implies that drug testing is justifiable. The defense of drug testing will have

to come from other grounds. The argument is based on an irrelevant comparison.

13. This is a false analogy..

17. This is a false analogy.

22. This is a false analogy.23. This is a good analogical argument. 4

24. These kinds of analogies often have a further point. In this case the author is trying to persuade us that Walker

"has given aid and comfort to those seeking to dismantle the greatness of art by turning it into a particularly

pernicious branch of advertising, the better to control it through the politics of the marketplace." I think what Link is

trying to say is that art should not be seen as propaganda, as a set of commercials for ideas. He doesn’t think art or

society is served very well if every work of art is reduced to an offensive idea in the eyes of its interpreters. It is a

dangeraous practice to interpret every work of art as a "message" about every topic it touches, or can be stretched to

touch, by an imaginative interpreter. Every work of art becomes just more grist for the mill for the perpetually

offended. The Venus de Milo offends one feminist for its glorification of the mutilation of women; the Mona Lisa

offends the cross-dresser who feels the artist is portraying in a demeaning way a man dressed as a woman; the whole

Sistine chapel--nay, most of Italy--becomes an offensive commercial for religious fantacies and the evil which has

come of them (according to some non-Christians); etc.

Finally, Link has one further point: Walker has no right being indignant at those who interpret her art using thesame reductionist method of interpretation she used regarding the award she was given. I don’t think he is calling

Walker a hypocrite. I think he is suggesting she rethink her views on art and propaganda. He also, of course, takes it

for granted that art shouln’t be propaganda.The state of California thinks differently. It not only lifted Walker’s story

from its test, it lifted another story which had a vegetarian character in it. The state’s reason: it was lifted on the

grounds that it might upset some meat eaters!

Link’s comparison of Walker’s reaction to the statuette to the Christian conservatives’ reaction to her

short story is relevant and a sound one. Good analogy.

CHAPTER EIGHT - CAUSAL REASONING

EXERCISE 8-5

1 true2 true

3 false

4 false

5 true

6 false7 true

8 true

9 true

10 true

11 false12 true

13 false

14 true

15 false

16 false17 false

18 false

19 true

20 true

21 false22 false

23 false

24 true

25 true

26 false


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EXERCISE 8-3

1.1. This is a weaker conclusion than the original one. The argument is therefore strengthened. (Generally speaking,

the weaker the conclusion, the less evidence needed to support it; and the stronger the conclusion, the more evidence

needed to support it.)1.2. This would eliminate being able to control for relevant causal factors. It would weaken the argument.

1.3. The control group and experimental group must be alike in all relevant respects except for the factor being

tested. This would weaken the argument.

1.4. The increase in the number of cases showing the effect would increase the strength of the argument.

1.5. The increase in the number of rats would strengthen the argument, providing the percentages of rats showing the

tumors remained the same. However, using ten times as many rats will not strengthen the argument ten times!

1.6. This is a weaker conclusion than the original; it strengthens the argument.

1.7. This introduces a loss in control over potential factors being introduced which might be causing the difference in

effects. It weakens the argument.

1.8. Same as 1.7. Perhaps the x-rays are a significant causal factor in the development of the tumors.

1.9. If you did not know this, it would increase the number of significant similarities between humans and laboratory

animals from your point of view and would thus strengthen the argument.

1.10. This conclusion actually is two conclusions. One is that saccharin may increase the risk of bladder cancer forthe offspring of women who use it during pregnancy. That conclusion may appear to be weaker than the original one,

but it is actually stronger, since the original study involved offspring who were fed a saccharin diet--a very unlikely

parallel for humans. The other conclusion is that pregnant women should be given a warning that using saccharin

during pregnancy "may increase the risk that their child will develop bladder cancer." Whether this warning is

warranted or not is debatable.

EXERCISE 8-4

1. Post hoc fallacy. Because of the difficulty in controlling for potential causal factors, a prospective study on large

numbers of people with different degrees of acne might be best.

6. False cause. Correlation does not prove causality. It probably would be more sensible to produce a

counterargument than to do a scientific study to determine whether or not there is a causal connection between foodadditives and violent crime. Also, `food additives’ covers a wide variety of substances.

10. In testing the claim cowpox causes an immunity to smallpox by inoculating human beings is unimaginable today.

A controlled experiment would have meant inoculating with smallpox another group of humans who had not been

infected with cowpox. Since the test is for immunity, both the experimental and control groups get inoculated. The

experimental group is infected with smallpox; the control group is not. Such an experiment would probably have led

to the deaths of most, if not all, of those in the control group. A prospective study would have gathered a large

random sample, divided the sample into two groups: one which had been infected with cowpox and one which had

not. Over time, the incidence of smallpox should be significantly greater in the group not infected with cowpox, if it

is true that cowpox causes an immunity to smallpox. Apparently, Jenner was reasoning by a retrospective analysis. A

number of people don’t die of smallpox but they are just as exposed to it as those who do die. Comparing those who

show this effect with others like them who don’t show the effect, it was common knowledge that dairymaids were all

in the first group. Being a dairymaid exposes one to cowpox. So, Jenner reasoned it was the cowpox which was the

causal factor in the dairymaid’s not getting smallpox.16. Why Dr. James did not study nervous drivers rather than string players is beyond me. Why introduce an analogy

when you don’t have to? The differences between playing a string instrument on stage and driving a car during a

driving test would seem to outweigh any similarities they might have. Thus, even if the oxyprenolol helped the string

players, it would be a stretch to conclude that it would help nervous drivers pass their driving test.

I must confess that I did not find the outcome very striking. For one thing, we are not told what the mean

improvement for the control group was, so we do not know whether a 5 percent improvement is significant.

Furthermore, since the samples were small, the one player with a 73 percent improvement and those with 30 percent


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232not only could account for the entire 5 percent group improvement, but they indicate that a good number of the

experimental group must have deteriorated.

Note the way the conclusion is worded: "the results suggest that some people might benefit greatly from such

medication." Sure, and some might not benefit greatly. In any case, the proper way to have done this study would

have been to have taken two groups of people who had failed their driving tests because of nervousness. Oxyprenolol

is given to the experimental group and a placebo is given to the control group. Neither the subjects nor the drivingevaluators should know who has been given the oxyprenolol. Such a study is called a double blind study. The study

should be a double blind study to eliminate any psychological effects on the part of subjects (if one thinks she’s been

given a beta-blocker, she might relax) and any bias on the part of the evaluator (if she knows the subject has been

given a beta-blocker she might evaluate him differently). If oxyprenolol is a significant causal factor in reducing

nervousness of drivers being tested, then we should see a significantly higher percentage of the experimental group

passing their driving tests.

CHAPTER NINE - SCIENCE AND PSEUDOSCIENCE

EXEERCISE 9-1

1 true2 true

3 false

4 false

5 false

6 false

7 true

8 false

9 false10 false

11 true

12 true

13 true

14 true

15 true

16 false

17 true18 false

19 true

20 true

21 false

22 true

23 false

24 true

25 false26 true

27 true

28 false

29 true

30 false

31 false

32 true

33 true34 true

35 true

36 false

37 true

38 true

39 true

40 true

41 true42 true

43 false

44 false

45 true

46 true

47 true

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Logic Answers